Orthogonal Frequency Division Multiplexing (OFDM) is a spread spectrum technology in which the available bandwidth is subdivided into a number of channels or carriers whose spectra are orthogonal to each other. Each carrier has a well defined peak frequency. Data are transmitted in the form of symbols that have a predetermined duration and encompass some number of carrier frequencies. The data transmitted on these carriers can be modulated in amplitude and/or phase, using modulation schemes such as Binary Phase Shift Key (BPSK), Quadrature Phase Shift Key (QPSK), or m-bit Quadrature Amplitude Modulation (m-QAM). In some cases, the spectrum of transmitted symbols is adapted to regulatory requirements using spectral filtering (e.g., a HAM radio band notch filter, or an out of band roll-off filter).